In article , Ignoramus5833 says...

5. I salvaged a 1/4 and 1/3 HP motors from two broken vacuum pumps
that I had. I would buy a 5/8" ID pulley on one of them. Would they be
able to spin up a 7.5 or 10 HP motor? Jim Rozen reportedly used a 1/4
HP pony to spin up a 7.5 HP motor, that makes me hopeful.

OK, the idler motor in that setup is *five* hp, and it is spun
up by a 1/8 hp repulsion-induction motor. It takes about one
second to do this.

6. How fast would the idler need to spin before I can remove the pony
and apply 220V to the idler input?

It should be real close, or slightly higher than nameplate speed
to mimimize the inrush currents that flow when you energize it.

7. Is there something that I forgot to ask?

You should ask about balancing capacitors and phase angle correction
capacitors. Also you really should have at least one contactor
in the setup which will drop out (self-holding) if you lose power
while the converter is running.

As a data point, my setup will easily start and plug-reverse one hp
load motors, and is powered off a 15 amp 240 volt branch ckt.

Jim


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